Stand structure of the emergent conifer Araucaria laubenfelsii) in maquis and rainforest,Mont Do,New Caledonia

Abstract Despite its small size, New Caledonia has a flora which includes 43 endemic species of conifer. This study examines the stand structure of the New Caledonian conifer, Araucaria laubenfelsii Corbasson, a species which occurs on ukramafic soils as an emergent tree in rainforest and in an unusual structural association with maquis vegetation. Fire and cyclone blow-down are the primary disturbances in the maquis, but fire is infrequent in the rainforests which is evident from the low proportion of fire scarred trees. Preliminary results show abundant seedlings and saplings of A. laubenfelsii both in maquis and forest. Size class distributions of individuals suggest that the species is continuously regenerating in the maquis and immature forests. Variability in the stand structure in maquis communities reflects the probable patchy nature of disturbance from small-scale fires and blow-down from tropical cyclones. In mature forests, Nothofagus codonandra (Baillon) Steenis is the dominant canopy species and ‘other tree species’ are continuously regenerating, while the size class distributions and basal area of A. laubenfelsii suggest that there is, at present, limited regeneration of this species. Tree ring counts indicate that individuals in forest areas grow at a slower rate than those in maquis, but attain greater age, probably as a result of greater protection from fire.     

Nickel levels in arthropods associated with Ni hyperaccumulator plants from an ultramafic site in New Caledonia

Arthropods (mainly insects) were collected from a forest site that contained at least six species of Ni hyperaccumulators. Whole body Ni analysis was performed for 12 arthropod taxa, two of which were studied at different life cycle stages. We found two Nitolerant insects. The pentatomid heteropteran Utana viridipuncta, feeding on fruits of the Ni hyperaccumulator Hybanthus austrocaledonicus, contained a mean of 2 600 μNi/g in nymphs and 750 μNi/g in adults. The tephritid fly Bactrocera psidii, feeding on pulp of Sebertia acuminata fruits that contained 6 900 μNi/g, contained 420 μNi/g as larvae that had evacuated their guts and significantly less (65 μNi/g) as adults. European honeybees (Apis mellifera) visiting flowers of the Ni hyperaccumulator H. austrocaledonicus contained significantly more Ni (8‐fold more) than those collected from flowers of Myodocarpus fraxinifolius, a non‐hyperaccumulator. Our results show that some insects feed on Ni hyperaccumulator plants and that their feeding mobilizes Ni into local food webs.     

Aerial flow of barley yellow dwarf viruses and of their vectors in western France

During the years 1989–1992 cereal aphids were caught alive in a low level (1.5 m high) suction trap operated in Le Rheu (Brittany, France) and tested for BYDV transmission. In most cases comparisons with data collected simultaneously by a 12.2 m suction trap operating in the same site resulted in good relationships between weekly catches at both heights. Results from transmission tests showed that: (i) the two main BYDV vectors were Rhopalosiphum padi and Metopolophium dirhodum during the years of experiment; (ii) PAV and MAV were the commonest viruses and RPV was relatively scarce; (iii) during spring M. dirhodum appeared to be the most important MAV vector and nearly as good a PAV vector as R. padi; (iv) during autumn R. padi was the only vector of the three viruses with mixed transmission allowing it to transmit also MAV probably by heteroencapsidation. To give an indication of the risk of infection, infectivity indices were calculated by multiplying the numbers of aphids caught by the 12.2 m suction trap by the proportion that were infective. These infectivity indices agreed with field records of primary infections.     

Mark–recapture cloning: a straightforward and cost‐effective cloning method for population genetics of single‐copy nuclear DNA sequences in diploids

We describe a simple protocol to reduce the number of cloning reactions of nuclear DNA sequences in population genetic studies of diploid organisms. Cloning is a necessary step to obtain correct haplotypes in such organisms, and, while traditional methods are efficient at cloning together many genes of a single individual, population geneticists rather need to clone the same locus in many individuals. Our method consists of marking individual sequences during the polymerase chain reaction (PCR) using 5′‐tailed primers with small polynucleotide tags. PCR products are mixed together before the cloning reaction and clones are sequenced with universal plasmid primers. The individual from which a sequence comes from is identified by the tag sequences upstream of each initial primer. We called our protocol mark–recapture (MR) cloning. We present results from 57 experiments of MR cloning conducted in four distinct laboratories using nuclear loci of various lengths in different invertebrate species. Rate of capture (proportion of individuals for which one or more sequences were retrieved) and multiple capture (proportion of individuals for which two or more sequences were retrieved) empirically obtained are described. We estimated that MR cloning allowed reducing costs by up to 70% when compared to conventional individual‐based cloning. However, we recommend to adjust the mark:recapture ratio in order to obtain multiple sequences from the same individual and circumvent inherent technical artefacts of PCR, cloning and sequencing. We argue that MR cloning is a valid and reliable high‐throughput method, providing the number of sequences exceeds the number of individuals initially amplified.     

Microbial communities of ultramafic soils in maquis and rainforest at Mont Do,New Caledonia

We analysed variation in microbial community richness and function in soils associated with a fire‐induced vegetation successional gradient from low maquis (shrubland) through tall maquis to rainforest on metal‐rich ultramafic soils at Mt Do, New Caledonia. Random amplified polymorphic DNA fingerprinting was used to determine the extent of genetic relatedness among the microbial communities and indicated that the open and tall maquis microbial communities were more similar to each other than they were to the rainforest community. Sole‐source carbon utilization indicated variation in the microbial communities, again with greater diversity in rainforest soils. Plate counts showed that both rainforest and maquis soils contained bacteria that can grow in the presence of up to 20 mmol L^?1 nickel and 10 mmol L^?1 chromium. Understanding microbial community composition and dynamics in these ultramafic soils may lead to a better understanding of the processes facilitating vegetation succession from shrubland to forest on these high‐metal substrates, and of approaches to successful revegetation following mining for metals including nickel, chromium and cobalt.     

pasos (parental allocation of singles in open systems): a computer program for individual parental allocation with missing parents

pasos is a parental allocation program designed to identify collected parents based on individual multilocus genotypes while detecting missing parents when a proportion of them have not been collected. It makes use of restricted error tolerance in order to distinguish between a partially incorrect genotype from a false parent's genotype. pasos also introduces the technique of sequence allocation allowing the user to obtain estimates of the proportion of missing parents and of allocation correctness. The pasos interface is very similar to the one found in papa , its closed system counterpart ( Duchesne et al. 2002 ). A help file thoroughly describes all technical terms such as error modelling, parameters and procedures. pasos can be downloaded free of charge from: http://www.bio.ulaval.ca/louisbernatchez/ .     

Threatened plants of New Caledonia: Is the system of protected areas adequate?

With 76% of its 3063 native species of flora endemic, the New Caledonia biodiversity hotspot has long been recognized as having a high potential for conservation. Under the new IUCN Red List categories, 25% of the endemic plants are at risk (Conservation Dependent, Vulnerable, Endangered, Critically Endangered), and five species are already extinct. A review of their distribution demonstrates that 83% of the threatened species do not occur at all in a conservation area, and only 11% have their conservation status improved by a protected area. The protected area network is geographically and floristically very unbalanced, with the rainforest and high altitude maquis in the south concentrating most of the conservation effort. Conversely, the middle and northern segments of the island, as well as all of the dry west coast, are left without adequate conservation area. Two vegetation types, the sclerophyll forest and the unique low/middle altitude maquis, are virtually totally unprotected. We conclude that the current network of protected areas needs to be considerably expanded, in terms of both geographical/floristic subregions within New Caledonia and vegetation type covered. With only 54% of the conservation area covered by strict mining restrictions, existing reserves need to have their conservation efficiency improved by a more vigorous enforcement of their status, and by extending mining bans to all of them.